This invention relates to accelerators that may be useful for energy polymerizable compositions comprising a cationically curable material; energy-polymerizable compositions that comprise a cationically curable material and a two-component initiator system, which initiator system comprises at least one organometallic complex salt and at least one accelerator; and a method for curing the compositions. This invention also relates to preparing articles comprising the cured compositions. In addition to other uses, the compositions are useful as molded articles, as coating compositions including abrasion resistant coatings, as adhesives including structural adhesives, and as binders for abrasives and magnetic media. The invention also relates to compositions of matter comprising an organometallic complex salt and at least one compound selected from the Class 1 and Class 2 compounds disclosed herein.
Transition metal salts comprising an organometallic cation and a non-nucleophilic counteranion have been shown to have utility as photochemically activated initiators for cationic addition polymerization. These photoinitiator salts include (cyclopentadienyl) (arene) iron+ salts of the anions PF6xe2x88x92 and SbF6xe2x88x92. Similarly, certain classes of these salts are known to be thermally-activatable curatives for cationic polymerizations.
For many commercial applications, the monomers being polymerized are often multifunctional (i.e., contain more than one polymerizable group per molecule), for example, epoxides, such as diglycidyl ethers of bisphenol A (DGEBA). Mixtures of multifunctional monomers such as epoxides and polyalcohols (polyols) or polyepoxides and polyalcohols can undergo acid-catalyzed polycondensation via a step-growth mechanism. Also included in this description are multireactive monomersxe2x80x94those that comprise two or more classes of reactive groups.
In many applications photoinduced polymerization is impossible, impractical or undesirable. For example, many situations where polymerization reactions occur in a closed environment (i.e., in a mold or in a laminated product) or where polymerizable compositions may contain opacifying pigments, thermally activated initiators are preferred. Thermally-activated initiators, such as known organometallic salts, may be used to initiate polymerization in these cases.
There is a continuing need to be able to modify the rate and temperature of polymerization of energy polymerizable compositions to meet the needs of specific applications.
The present invention relates to accelerators that may be used to influence the temperature at which the polymerization of an energy polymerizable composition comprising a cationically curable material occurs. In particular, the accelerators of this invention may be used to reduce the polymerization temperature or allow modification of the rate or degree of polymerization at a given temperature of cationically-polymerizable materials when organometallic salt initiators are used in cationic polymerization.
Briefly, in one aspect, this invention provides a method comprising the step of using an accelerator and at least one salt of an organometallic complex cation to increase the rate, or reduce the temperature, of cure of an energy polymerizable composition comprising a cationically curable material, wherein said cation contains at least one carbon atom bonded to a transition metal atom, and wherein said accelerator, or an active portion thereof, comprises at least one compound selected from classes 1 and 2
class 1 comprises compounds represented by Formula III, and
class 2 comprises compounds represented by Formula IV.
In another aspect this invention provides an energy polymerizable composition comprising:
(a) at least one cationically curable material;
(b) a two-component initiator system comprising:
(1) at least one salt of an organometallic complex cation, wherein said cation contains at least one carbon atom bonded to a transition metal atom, and
(2) at least one accelerator, or an active portion thereof, of classes 1 and 2 wherein class 1 comprises compounds represented by Formula III herein and class 2 comprises compounds represented by Formula IV herein.
In other aspects, the invention provides an energy polymerizable composition with one or more of the following optional components:
(a) at least one of an alcohol-containing material and additional adjuvants;
(b) stabilizing ligands to improve shelf-life;
(c) at least one film-forming thermoplastic oligomeric or polymeric resin essentially free of nucleophilic groups, such as amine, amide, nitrile, sulfur, or phosphorous functional groups or metal-complexing groups, such as carboxylic acid and sulfonic acid; and
(d) coupling agents to modify adhesion.
In another aspect, the invention provides a process for controlling or modifying the cure of a composition comprising the steps of:
(a) providing the energy polymerizable composition of the invention,
(b) adding sufficient energy to the composition in the form of at least one of heat, radiation, and light, in any combination and order, to polymerize the composition.
In another aspect, this invention provides an article comprising a substrate having on at least one surface thereof a layer of the composition of the invention. The article can be provided by a method comprising the steps:
(a) providing a substrate,
(b) coating the substrate with the curable composition of the invention and, optionally, adjuvants; and
(c) supplying sufficient energy to the composition in the form of at least one of heat, radiation, and light in any combination and order to polymerize the composition.
In another aspect, this invention provides a composition of matter comprising
(1) at least one salt of an organometallic complex cation, wherein said cation contains at least one carbon atom bonded to a transition metal atom, and
(2) at least one compound, or an active portion thereof, from classes 1 and 2 wherein class 1 comprises compounds represented by Formula III herein and class 2 comprises compounds represented by Formula IV herein.
As used in this application:
xe2x80x9cenergy-induced curingxe2x80x9d means curing or polymerization by means of heat, light (e.g., ultraviolet, visible) or radiation, (e.g., electron beam), or light in combination with heat means, such that heat and light are used simultaneously, or in any sequence, for example, heat followed by light, light followed by heat followed by light;
xe2x80x9ccatalytically-effective amountxe2x80x9d means a quantity sufficient to effect polymerization of the curable composition to a polymerized product at least to a degree to cause an increase in viscosity of the composition under the conditions specified;
xe2x80x9corganometallic saltxe2x80x9d means an ionic salt of an organometallic complex cation, wherein the cation contains at least one carbon atom of an organic group that is bonded to a metal atom of the transition metal series of the Periodic Table of Elements (xe2x80x9cBasic Inorganic Chemistryxe2x80x9d, F. A. Cotton, G. Wilkinson, Wiley, 1976, p. 497);
xe2x80x9cinitiatorxe2x80x9d and xe2x80x9ccatalystxe2x80x9d are used interchangeably and mean at least one salt of an organometallic complex cation that can change the speed of a chemical reaction;
xe2x80x9ccationically curable monomerxe2x80x9d means at least one epoxide containing or vinyl ether containing material;
xe2x80x9cpolymerizable compositionxe2x80x9d or xe2x80x9ccurable compositionxe2x80x9d as used herein means a mixture of the initiator system and the cationically curable monomer; alcohols and adjuvants optionally can be present;
xe2x80x9cpolymerizexe2x80x9d or xe2x80x9ccurexe2x80x9d means to supply sufficient energy to a composition in the form of at least one of heat and light in any order or combination to alter the physical state of the composition, to make it transform from a fluid to less fluid state, to go from a tacky to a non-tacky state, to go from a soluble to insoluble state, or to decrease the amount of polymerizable material by its consumption in a chemical reaction;
xe2x80x9cinitiation systemxe2x80x9d, xe2x80x9cinitiator systemxe2x80x9d, or xe2x80x9ctwo-component initiatorxe2x80x9d means at least one salt of an organometallic complex cation and at least one accelerator, the system being capable of initiating polymerization;
xe2x80x9cacceleratorxe2x80x9d or xe2x80x9caccelerating additivexe2x80x9d means at least one of specified classes of compounds that moderate the cure of a composition of the invention by reducing the polymerization temperature or allowing an increase of the rate or degree of polymerization at a given temperature;
xe2x80x9cepoxy-containingxe2x80x9d means a material comprising at least one epoxy and may further comprise accelerating additives, stabilizing additives, fillers, diols, and other additives;
xe2x80x9cgroupxe2x80x9d or xe2x80x9ccompoundxe2x80x9d or xe2x80x9cligandxe2x80x9d means a chemical species that allows for substitution or which may be substituted by conventional substituents which do not interfere with the desired product, e.g., substituents can be alkyl, alkoxy, aryl, phenyl, halo (F, Cl, Br, I), cyano, nitro, etc., and
xe2x80x9cepoxy/polyolxe2x80x9d and xe2x80x9ccatalyst/additivexe2x80x9d, etc., mean combinations of the substances on both sides of the slash (xe2x80x9c/xe2x80x9d).
An advantage of at least one embodiment of the present invention is that the initiator system can initiate curing of a thermally- or photo- polymerizable composition at temperatures lower than temperatures required for reactions initiated without the accelerators of the present invention.
Another advantage of at least one embodiment of the invention is that the initiator system can provide enhanced curing of a thermally- or photo-polymerizable composition at a given temperature. For example, at a given temperature, curing time can be reduced as compared to curing times for reactions initiated without the accelerators of the invention.
Yet another advantage of at least one embodiment of the invention is the ability to affect a color change in the curable composition upon activation of a catalyst in the composition or as the composition changes from an uncured to a cured state.